Leak tracing

Details Leak tracing Leak tracing

1999-05-19

2001-11-13

Larkin, Daniel S. (Department: 2856)

Measuring and testing

With fluid pressure

Leakage

C073S04050R, C073S865800

Reexamination Certificate

active

06314795

ABSTRACT:

TECHNICAL FIELD
This invention relates to a method of, and apparatus for, leak testing of fluid from a pipeline.
Leakage of fluid from a pipeline can be costly, and in the case of a hazardous fluid be dangerous, when the fluid can leak from, and so cease to be protected by, the pipeline. Such leakage can also lead to environmental problems in the region of the leakage. Where the pipeline is above ground, then periodic detailed inspection of the pipeline can lead to the identification of a leak. When the pipeline is buried or otherwise obscured from sight, then identification of a leak is more difficult and without sophisticated inspection procedures small leaks may continue for an extended period without detection. Even when detected with currently available procedures, identifying the exact location of a leak may not be possible; and in order to gain access to a specific leak it may be necessary to excavate and expose the pipe over some distance.
DISCLOSURE OF THE INVENTION
According to a first aspect of the present invention, there is provided a method of leak detection in a pipeline wherein fluid can be conveyed along the pipeline by a pressure differential in the fluid established between a first and a second part of the pipeline characterised by the steps of:
1 reducing the pressure differential;
2 providing an opening in the pipeline between the first part (P
1
) and second part (P
2
) to allow access to the interior of the pipeline (W);
3 introducing into the pipeline (W) at the opening an initially loose fitting plug (
11
) having at least an expandable periphery (
21
) adopted for inflation by means of a flexible pipe (
23
) connected at one end to the plug (
11
);
4 providing along the length of the flexible pipe (
23
) tracing means (
31
) whereby the path of the flexible pipe (
23
), at least while within a pipeline (W), can be detected remotely;
5 closing the opening in the pipeline (W) to restore the ability of the pipeline (W) to maintain a pressure differential between the first part (P
1
) and second part (P
2
);
6 allowing the plug (
11
) to be driven along the pipeline (W) by a fluid pressure differential established by fluid in the pipeline across the plug (
11
) while governing motion of the plug (
11
) by means of the flexible pipe (
23
);
7 inflating the expandable periphery (
21
) of the plug (
11
) so as to drive the periphery (
21
) into fluid tight engagement with the wall (
12
′) of the pipeline (W) so as to substantially block the flow of fluid along the pipeline (W) from an upstream side (U) of the plug (
11
) to the downstream side (D) and cause the plug (
11
) to be locked in position within the pipeline (W);
8 establishing either:
whether fluid pressure in the pipeline (W) upstream (U) of the plug (
11
): remains constant, implying that no leakage exists upstream (U) of the plug (W) between the plug (
11
) and the first part (P
1
) of the pipeline (W); or falls, implying that a leak (X) through the pipeline wall exists between the plug (W) and the first part (P
1
) of the pipeline; or
whether flow continues along the pipeline implying that a leak (X) through the pipeline wall exists between the plug (W) and the first part (P
1
) of the pipeline; and
9 remotely detecting the position of the plug (
11
) while locked in position; and relating it to the position of the leak (X).
According to a first preferred version of the first aspect, characterised in that following step eight there is provided the further step of deflating the expandable periphery (
21
) of the plug (
11
) so as to release the periphery (
21
) from fluid tight engagement with the wall (
12
′) and using the flexible pipe (
23
) to govern the positioning of the plug (
11
) at a new location to enable steps seven and eight to be repeated until a leak position (X) in the pipeline is established to a required extent for identification of the position of the leak (X) typically to provide for subsequent rectification of the leak (X).
According to a second preferred version of the first aspect of the present invention or the first preferred version thereof, the method is further characterised in that the expandable periphery (R,
FIG. 5
) is formed integrally with a front section (
102
) to the plug (
101
) located at opposite end (
103
) of the plug (
101
) to the one end thereof and the expansion of the periphery (R) leads to corresponding expansion of the front section (
105
) of the plug. Typically, the wall thickness (V) of the expandable periphery (R) and/or the front section (
105
) of the plug (
101
) is varied so as to provide for local changes in shape when expanded relative to at least some other part of the expandable periphery and/or front section (
105
).
According to a second aspect of the present invention, there is provided apparatus for leak detection in a pipeline wherein fluid can be conveyed along the pipeline by a pressure differential in the fluid established between a first and a second part of the pipeline characterised by:
1 a plug (
11
,
101
) for insertion in to the pipeline (
12
), the plug (
11
,
101
) having a first working configuration and a second working configuration across a longitudinal axis (A) of the plug (
11
,
101
); in the first configuration the outside diameter (D) of the plug provides a first working diameter for the plug somewhat less than a bore (D′) of a pipeline (
12
) into which the plug is be located for use; in the second working configuration the outside diameter (S) of the plug (
21
) increases to provide a resilient interference fit for the plug (
11
) in a pipeline (
12
) into which the plug
11
) is to be located for use;
2 the plug (
11
) incorporating a peripheral inflatable sleeve (
21
) around a duct (
26
) in the plug (
12
) the sleeve
21
), in a substantially un-inflated configuration, serving to define the first working condition of the plug (
12
) and in an inflated configuration serving to define the second working condition of the plug;
3 a flexible line (
23
) having a first end (
22
) anchored to the plug (
12
) and communicating with the duct (
26
) to enable the sleeve (
21
) to be pressurised by fluid fed to the duct (
26
) by means of the flexible line (
23
); the flexible line (
23
) serving to control motion of the plug (
11
) when in a pipeline (W); and
4 tracing means (
31
) incorporated in or supported by the flexible line (
23
) whereby the path of the flexible pipe (
23
), at least while within a pipeline (W), can be detected remotely from outside the pipeline (W).
According to a first preferred version of the second aspect of the present invention, the apparatus is further characterised in that the plug (
11
) is in the form of a bullet shaped member having an internal duct (
26
) and a front section (
13
) and rear section (
14
) spaced by an intermediate section (
16
); the first section (
13
) and/or second section (
16
) having an outside diameter (D) corresponding to the first working diameter; the intermediate section (
16
) incorporating the peripheral inflatable sleeve (
21
) of flexible material serving to define a wall of the internal duct (
26
); the inner side of the sleeve (
21
) being pressurisable by way of the duct (
26
,
28
) to urge the sleeve (
21
) outwardly into the second working configuration of the plug (
11
) wherein the sleeve
921
) serves to provide an outside diameter D′) corresponding to the second working diameter of the plug (
11
). Typically, the plug (
101
) is in the form of a bullet shaped member having an internal duct (
109
) and an integral front and sleeve section (
102
) of resilient material mounted on a tail unit (
103
); the integral section (
102
) having an outside diameter corresponding to the first working diameter; the integral section (
102
) incorporating the peripheral inflatable sleeve (
102
) of flexible material serving to define a wall of the internal duct; the inner side of the integral section
102
being pressurisable by way of the duct (
109
) to urge at least the sleeve part of the integral section (
102
) outwardly

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